Embodiments of the invention generally relate to circuit breakers and electronic trip units, and more particularly to automatic breaker rating in circuit breakers and/or electronic trip units.
Circuit breakers may be used in industrial, commercial, and residential applications for protecting electrical devices from over-current situations. Circuit breakers, trip units, and/or electronic trip units with circuit breakers may measure electrical current of a load using a secondary current. The secondary current may be derived from the electrical current of the load through current transformers (CT) and/or Rogowski sensors. CTs and Rogowski sensors provide reduced current proportional to the electrical current of the load. The reduced current (noted secondary current above) may be used by the circuit breaker to perform protection analysis, metering, and other functionality included in the circuit breaker.
Circuit breakers may be used as a replacement for conventional fuses, although some circuit breakers function slower than fuses, and may include complicated mechanical components. However, fusing provides only a single level of protection. That is, fuses are generally non-adjustable. However, circuit breakers may be rated for many applications, and may be de-rated to increase breaker selectivity. For example, a circuit breaker rated to switch up to 100 amps may be adjusted to trip at 30 amps. However, this may require physically swapping rating plugs and setting internal gains for detection devices within the circuit breaker for the new trip setting. It is appreciated that this requires an operator to identify and adjust the de-rating current level as necessary for each application, save these setting in the circuit breaker (or trip unit), and test to ensure proper and accurate current level tripping.
Accordingly, there is a need in the art for an electronic control of a circuit breaker having an adjustable breaker rating that overcomes these drawbacks.